Behaviour for challenge types, and the struct handed to templates.

A challenge type generates a public map (rendered to the user) and a secret (kept inside the encrypted token), checks a response against the secret, and renders its own UI.

Writing a challenge type

defmodule MyApp.ColorChallenge do
  @behaviour Wiztchta.Challenge
  use Phoenix.Component

  @impl true
  def generate(_opts), do: {%{"question" => "Type the word blue"}, "blue"}

  @impl true
  def valid?(secret, response, _opts), do: String.downcase(String.trim(response)) == secret

  @impl true
  def render(assigns) do
    ~H"""
    <label for={@id <> "-response"}>{@challenge.public["question"]}</label>
    <input type="text" id={@id <> "-response"} name={@name <> "[response]"} />
    """
  end
end

render/1 receives @challenge (this struct), @id (DOM id prefix) and @name (form param prefix). The response must be submitted as @name <> "[response]"; the token input is rendered for you.

Secrets are stored with :erlang.term_to_binary/1, so keep them small.